Well, I am surprised! I honestly thought that nutritional labelling was compulsory but in fact it isn't. Only if the manufacturer is making specific health claims for the product is it compulsory to put the nutritional information on.
New legislation will come into force in December 2014 which will mean that nutritional labelling will be mandatory, but there are exceptions, one of them being "Unprocessed products that comprise a single ingredient or category of ingredients", which I assume would include the turkey steaks you are referring to.
So Waitrose aren't breaking any rules, but it's still jolly inconvenient to have the labelling where you can't read it until you get home!